The long-range goal of the proposed research is to elucidate the mechanisms which regulate the biosynthesis of the fatty acids which provide the fatty acyl chains of the major lipid classes (structural and storage) im mammalian cells. One immediate objective is to focus on the enzyme acetyl CoA carboxylase (ACC), which plays a critical role in the biosynthesis of these fatty acids, and to elucidate the molecular mechanisms underlying the regulation of the activity and content of this key enzyme in mammalian tissues. We will attempt to resolve an ACC complex into functional subunits analogous to those previously isolated from Escherichia coli. The isolated subunits, including the biotin carboxyl carrier protein component, will be characterized with respect to their catalytic and regulatory functions. A second objective will be to study the role of phospholipases in thermal control of fatty acyl chain metabolism in a eukaryotic plasma membrane. For these studies a wall-less mutant of Neurospora crassa will be used, since highly purified plasma membranes can be isolated from this organism using a concanavalin A binding procedure. BIBLIOGRAPHIC REFERENCES: Fall, R. R. and P. R. Vagelos, "Biotin carboxyl carrier protein from Escherichia coli," Methods Enzymol. XXXVB, 17-25 (1975). Fall, R. R., A. W. Alberts, and P. R. Vagelos, "Analysis of bacterial biotin-proteins," Biochim. Biophys. Acta 379, 496-503 (1975).